- NAME
- SYNOPSIS
- DESCRIPTION
- RETURN VALUES
- VERIFICATION FLAGS
- NOTES
- BUGS
- EXAMPLE
- SEE ALSO
- HISTORY

# NAME

X509_VERIFY_PARAM_set_flags, X509_VERIFY_PARAM_clear_flags, X509_VERIFY_PARAM_get_flags, X509_VERIFY_PARAM_set_purpose, X509_VERIFY_PARAM_set_trust, X509_VERIFY_PARAM_set_depth, X509_VERIFY_PARAM_get_depth, X509_VERIFY_PARAM_set_time, X509_VERIFY_PARAM_add0_policy, X509_VERIFY_PARAM_set1_policies, X509_VERIFY_PARAM_set1_host, X509_VERIFY_PARAM_add1_host, X509_VERIFY_PARAM_set_hostflags, X509_VERIFY_PARAM_get0_peername, X509_VERIFY_PARAM_set1_email, X509_VERIFY_PARAM_set1_ip, X509_VERIFY_PARAM_set1_ip_asc - X509 verification parameters

# SYNOPSIS

     #include <openssl/x509_vfy.h>

     int X509_VERIFY_PARAM_set_flags(X509_VERIFY_PARAM *param, unsigned long flags);
     int X509_VERIFY_PARAM_clear_flags(X509_VERIFY_PARAM *param,
                                                            unsigned long flags);
     unsigned long X509_VERIFY_PARAM_get_flags(X509_VERIFY_PARAM *param);

     int X509_VERIFY_PARAM_set_purpose(X509_VERIFY_PARAM *param, int purpose);
     int X509_VERIFY_PARAM_set_trust(X509_VERIFY_PARAM *param, int trust);

     void X509_VERIFY_PARAM_set_time(X509_VERIFY_PARAM *param, time_t t);

     int X509_VERIFY_PARAM_add0_policy(X509_VERIFY_PARAM *param,
                                                    ASN1_OBJECT *policy);
     int X509_VERIFY_PARAM_set1_policies(X509_VERIFY_PARAM *param,
                                            STACK_OF(ASN1_OBJECT) *policies);

     void X509_VERIFY_PARAM_set_depth(X509_VERIFY_PARAM *param, int depth);
     int X509_VERIFY_PARAM_get_depth(const X509_VERIFY_PARAM *param);

     int X509_VERIFY_PARAM_set1_host(X509_VERIFY_PARAM *param,
                                     const char *name, size_t namelen);
     int X509_VERIFY_PARAM_add1_host(X509_VERIFY_PARAM *param,
                                     const char *name, size_t namelen);
     void X509_VERIFY_PARAM_set_hostflags(X509_VERIFY_PARAM *param,
                                          unsigned int flags);
     char *X509_VERIFY_PARAM_get0_peername(X509_VERIFY_PARAM *param);
     int X509_VERIFY_PARAM_set1_email(X509_VERIFY_PARAM *param,
                                     const char *email, size_t emaillen);
     int X509_VERIFY_PARAM_set1_ip(X509_VERIFY_PARAM *param,
                                   const unsigned char *ip, size_t iplen);
     int X509_VERIFY_PARAM_set1_ip_asc(X509_VERIFY_PARAM *param, const char *ipasc);

# DESCRIPTION

These functions manipulate the X509_VERIFY_PARAM structure associated with a certificate verification operation.

The `X509_VERIFY_PARAM_set_flags()` function sets the flags in param by oring it with flags. See the VERIFICATION FLAGS section for a complete description of values the flags parameter can take.

`X509_VERIFY_PARAM_get_flags()` returns the flags in param.

`X509_VERIFY_PARAM_clear_flags()` clears the flags flags in param.

`X509_VERIFY_PARAM_set_purpose()` sets the verification purpose in param to purpose. This determines the acceptable purpose of the certificate chain, for example SSL client or SSL server.

`X509_VERIFY_PARAM_set_trust()` sets the trust setting in param to trust.

`X509_VERIFY_PARAM_set_time()` sets the verification time in param to t. Normally the current time is used.

`X509_VERIFY_PARAM_add0_policy()` enables policy checking (it is disabled by default) and adds policy to the acceptable policy set.

`X509_VERIFY_PARAM_set1_policies()` enables policy checking (it is disabled by default) and sets the acceptable policy set to policies. Any existing policy set is cleared. The policies parameter can be NULL to clear an existing policy set.

`X509_VERIFY_PARAM_set_depth()` sets the maximum verification depth to depth. That is the maximum number of untrusted CA certificates that can appear in a chain.

`X509_VERIFY_PARAM_set1_host()` sets the expected DNS hostname to name clearing any previously specified host name or names. If name is NULL, or empty the list of hostnames is cleared, and name checks are not performed on the peer certificate. If name is NUL-terminated, namelen may be zero, otherwise namelen must be set to the length of name. When a hostname is specified, certificate verification automatically invokes X509_check_host(3) with flags equal to the flags argument given to X509_VERIFY_PARAM_set_hostflags() (default zero). Applications are strongly advised to use this interface in preference to explicitly calling X509_check_host(3), hostname checks are out of scope with the DANE-EE(3) certificate usage, and the internal check will be suppressed as appropriate when DANE support is added to OpenSSL.

`X509_VERIFY_PARAM_add1_host()` adds name as an additional reference identifer that can match the peer's certificate. Any previous names set via `X509_VERIFY_PARAM_set1_host()` or `X509_VERIFY_PARAM_add1_host()` are retained, no change is made if name is NULL or empty. When multiple names are configured, the peer is considered verified when any name matches.

`X509_VERIFY_PARAM_get0_peername()` returns the DNS hostname or subject CommonName from the peer certificate that matched one of the reference identifiers. When wildcard matching is not disabled, or when a reference identifier specifies a parent domain (starts with ``.'') rather than a hostname, the peer name may be a wildcard name or a sub-domain of the reference identifier respectively. The return string is allocated by the library and is no longer valid once the associated param argument is freed. Applications must not free the return value.

`X509_VERIFY_PARAM_set1_email()` sets the expected RFC822 email address to email. If email is NUL-terminated, emaillen may be zero, otherwise emaillen must be set to the length of email. When an email address is specified, certificate verification automatically invokes X509_check_email(3).

`X509_VERIFY_PARAM_set1_ip()` sets the expected IP address to ip. The ip argument is in binary format, in network byte-order and iplen must be set to 4 for IPv4 and 16 for IPv6. When an IP address is specified, certificate verification automatically invokes X509_check_ip(3).

`X509_VERIFY_PARAM_set1_ip_asc()` sets the expected IP address to ipasc. The ipasc argument is a NUL-terminal ASCII string: dotted decimal quad for IPv4 and colon-separated hexadecimal for IPv6. The condensed ``::'' notation is supported for IPv6 addresses.

# RETURN VALUES

X509_VERIFY_PARAM_set_flags(), X509_VERIFY_PARAM_clear_flags(), X509_VERIFY_PARAM_set_purpose(), X509_VERIFY_PARAM_set_trust(), `X509_VERIFY_PARAM_add0_policy()` X509_VERIFY_PARAM_set1_policies(), X509_VERIFY_PARAM_set1_host(), X509_VERIFY_PARAM_set_hostflags(), X509_VERIFY_PARAM_set1_email(), `X509_VERIFY_PARAM_set1_ip()` and `X509_VERIFY_PARAM_set1_ip_asc()` return 1 for success and 0 for failure.

`X509_VERIFY_PARAM_get_flags()` returns the current verification flags.

`X509_VERIFY_PARAM_set_time()` and `X509_VERIFY_PARAM_set_depth()` do not return values.

`X509_VERIFY_PARAM_get_depth()` returns the current verification depth.

# VERIFICATION FLAGS

The verification flags consists of zero or more of the following flags ored together.

X509_V_FLAG_CRL_CHECK enables CRL checking for the certificate chain leaf certificate. An error occurs if a suitable CRL cannot be found.

X509_V_FLAG_CRL_CHECK_ALL enables CRL checking for the entire certificate chain.

X509_V_FLAG_IGNORE_CRITICAL disabled critical extension checking. By default any unhandled critical extensions in certificates or (if checked) CRLs results in a fatal error. If this flag is set unhandled critical extensions are ignored. WARNING setting this option for anything other than debugging purposes can be a security risk. Finer control over which extensions are supported can be performed in the verification callback.

THe X509_V_FLAG_X509_STRICT flag disables workarounds for some broken certificates and makes the verification strictly apply X509 rules.

X509_V_FLAG_ALLOW_PROXY_CERTS enables proxy certificate verification.

X509_V_FLAG_POLICY_CHECK enables certificate policy checking, by default no policy checking is peformed. Additional information is sent to the verification callback relating to policy checking.

X509_V_FLAG_EXPLICIT_POLICY, X509_V_FLAG_INHIBIT_ANY and X509_V_FLAG_INHIBIT_MAP set the require explicit policy, inhibit any policy and inhibit policy mapping flags respectively as defined in RFC3280. Policy checking is automatically enabled if any of these flags are set.

If X509_V_FLAG_NOTIFY_POLICY is set and the policy checking is successful a special status code is set to the verification callback. This permits it to examine the valid policy tree and perform additional checks or simply log it for debugging purposes.

By default some additional features such as indirect CRLs and CRLs signed by different keys are disabled. If X509_V_FLAG_EXTENDED_CRL_SUPPORT is set they are enabled.

If X509_V_FLAG_USE_DELTAS ise set delta CRLs (if present) are used to determine certificate status. If not set deltas are ignored.

X509_V_FLAG_CHECK_SS_SIGNATURE enables checking of the root CA self signed cerificate signature. By default this check is disabled because it doesn't add any additional security but in some cases applications might want to check the signature anyway. A side effect of not checking the root CA signature is that disabled or unsupported message digests on the root CA are not treated as fatal errors.

The X509_V_FLAG_CB_ISSUER_CHECK flag enables debugging of certificate issuer checks. It is not needed unless you are logging certificate verification. If this flag is set then additional status codes will be sent to the verification callback and it must be prepared to handle such cases without assuming they are hard errors.

The X509_V_FLAG_NO_ALT_CHAINS flag suppresses checking for alternative chains. By default, when building a certificate chain, if the first certificate chain found is not trusted, then OpenSSL will continue to check to see if an alternative chain can be found that is trusted. With this flag set the behaviour will match that of OpenSSL versions prior to 1.0.2b.

The X509_V_FLAG_TRUSTED_FIRST flag causes chain construction to look for issuers in the trust store before looking at the untrusted certificates provided as part of the the peer chain. Though it is not on by default in OpenSSL 1.0.2, applications should generally set this flag. Local issuer certificates are often more likely to satisfy local security requirements and lead to a locally trusted root. This is especially important When some certificates in the trust store have explicit trust settings (see ``TRUST SETTINGS'' in x509(1)).

The X509_V_FLAG_PARTIAL_CHAIN flag causes intermediate certificates in the trust store to be treated as trust-anchors, in the same way as the self-signed root CA certificates. This makes it possible to trust certificates issued by an intermediate CA without having to trust its ancestor root CA. With OpenSSL 1.0.2, chain construction continues as long as there are additional trusted issuers in the trust store, and the last trusted issuer becomes the trust-anchor. Thus, even when an intermediate certificate is found in the trust store, the verified chain passed to callbacks may still be anchored by a root CA.

# NOTES

The above functions should be used to manipulate verification parameters instead of legacy functions which work in specific structures such as X509_STORE_CTX_set_flags().

# BUGS

Delta CRL checking is currently primitive. Only a single delta can be used and (partly due to limitations of X509_STORE) constructed CRLs are not maintained.

If CRLs checking is enable CRLs are expected to be available in the corresponding X509_STORE structure. No attempt is made to download CRLs from the CRL distribution points extension.

# EXAMPLE

Enable CRL checking when performing certificate verification during SSL connections associated with an SSL_CTX structure ctx:

      X509_VERIFY_PARAM *param;
      param = X509_VERIFY_PARAM_new();
      X509_VERIFY_PARAM_set_flags(param, X509_V_FLAG_CRL_CHECK);
      SSL_CTX_set1_param(ctx, param);
      X509_VERIFY_PARAM_free(param);

# SEE ALSO

X509_verify_cert, X509_check_host, X509_check_email, X509_check_ip, x509

# HISTORY

The X509_V_FLAG_NO_ALT_CHAINS flag was added in OpenSSL 1.0.2b